David E. Clement

Pattern uncertainty and the discrimination of visual patterns

Sixty Ss individually sorted eight decks of 50 cards each. A deck contained 25 cards each of two stimulus patterns. The patterns were drawn from different sets of five-dot patterns judged to be equivalent. The eight decks represented pairs of patterns drawn (a) from the same equivalence set, (b) from different equivalence sets of the same size, and (c) from different equivalence sets of different sizes. Sorting times were shown to increase with increasing size of equivalence set, and were shown to be greater for patterns drawn from within the same equivalence set than for patterns drawn from different equivalence sets. Ratings of pattern goodness were found to be useful predictors of sorting time only in their capacity to discriminate between equivalence sets of different sizes. The results were interpreted as supporting the importance of equivalence set membership in a discrimination task where the S logically does not have to consider stimuli other than the given criterion stimuli.

Sex composition and group performance in a visual signal detection task

Forty-eight Ss (24 males, 24 females) were run in groups of 4 on 720 trials of a 16-alternative forced-choice visual signal detection task requiring both individual and group decisions. Four types of groups were formed: all male, all female, mixed-alternate (seated in the order male-female-male-female), and mixed-adjacent (seated in the order male-male-female-female). There were no differences in performance between all-male and all-female groups, but mixed-sex groups had poorer performance, with mixed-adjacent groups having significantly lower sensitivity than homogeneous-sex groups. The results were interpreted as indicating that heterogeneity of groups with regard to sex interacts with seating pattern in affecting performance, probably due to the formation of information coalitions between like-sex group members when the seating pattern encourages such coalitions.

Instructions, strategies, and pattern uncertainty in a visual discrimination task

A card-sorting task involved discrimination of patterns from the same equivalence set, patterns from different sets of the same size, and patterns from different sets of different sizes. Instructions, experimental conditions, and the number of different patterns to be sorted into two trays were varied in an attempt to change Ss’ strategies from whole-pattern processing to single-element processing. Instructions alone were ineffectual in preventing whole-pattern processing, and physical masks over most of the criterion stimuli (patterns used as guides in sorting) were only somewhat effective. Differences among tasks that were attributable to size of equivalence set were eliminated only by arranging the stimuli so that a whole-pattern strategy required a great deal more information processing, or so that such a strategy could not lead to the required discrimination. The results were interpreted as confirming the influence of the properties of sets of stimuli, as well as the strength of the tendency of human Ss to process and categorize patterns in their entirety. nt]mis|This research was supported in part by a University Research Council grant.

No risky shift effect with real groups and real risks

Five discussion sections of an introductory psychology course (containing 16-18 students each) were asked to select an examination schedule from a set of eight alternatives. The choices had been scaled by students in a previous course on a risk-safety continuum and were selected for maximum dispersion on the continuum as well as for consistency in placement on the continuum. Individual preferences for schedule were obtained both before and after the group decision. Four of five groups shifted in a conservative direction from the average of initial individual choices. A significant proportion (.9) of those Ss who changed their individual preferences after discussion shifted in a conservative direction. The results suggest that the “risky-shift” effect is an artifact of the laboratory conditions under which it has been obtained.

Group Performance in a Visual Signal-Detection Task

Sixteen male subjects were run in groups of four on 720 trials of a 16-alternative, forced-choice, visual signal-detection task. The first and third blocks of 240 trials required individual judgments concerning target location. The second block of 240 trials required a group decision as to target location for two groups of subjects, and individual responses followed by a group decision for the other two groups. Comparisons were made among individual performance, real group performance, and the performance of two types of pseudogroup (derived from individual data) using an information-integration and a decision-threshold model. Group performance was better than individual performance, and was midway between the performances predicted by the two pseudogroup models, indicating that neither of the latter were adequate models for group performance. Real groups showed some characteristics both of independence and dependence among subjects, with some apparent use of logical decision rules in pooling individual information. Groups which made both individual and group responses on the second block of trials showed greater increases in sensitivity with practice than groups which made only group responses. It appeared that making individual responses had specific practice effects on subsequent individual performance, and these effects were greater in magnitude than the practice effects resulting from making group responses.

Scanning strategies and differential sensitivity in a visual signal detection task: Intrasubject reliability

Four Ss (two of each sex) were run on 960 trials of a 16-alternative forced-choice visual signal detection task. Analysis of variance of d’ values indicated the usual practice effects, as well as differential sensitivity to different target locations, and three significant interactions. Despite the significant changes in magnitude of d’, each S demonstrated consistency in the ordering of sensitivity as a function of target location across blocks of 320 trials (W =.51,.76,.85, and.81). The data imply extremely strong scanning biases which existed prior to the experimental task and further suggest that less than 400–500 trials is quite sufficient for reliable estimation of differential sensitivity among all 16 target locations in a 16-AFC task.

Parole and Probation Caseload Size Variation: The Florida Intensive Supervision Project

The widespread emphasis upon early release of convicted felons and misdemeanants led to investigation of the effects of variation in level of supervision of offenders subsequent to release. The authors describe a project in the State of Florida which included varying intensity of supervision for selected groups of probationers and parolees. The results indicated success in implementing the variations in supervision intensity; that is, the process measures were favorable. However, the product measures involving offender behavioral adjustment did not show clear advantages for either level of supervision intensity. Interpretations of the results depend heavily upon an understanding of the complexity of the justice system as well as the complex interaction of the behavioral causes.

Scanning strategies and differential sensitivity in a visual signal detection task: Intersubject consistency

Forty Ss (20 of each sex) were run individually for 480 trials of a 16-alternative forced-choice visual signal detection task. Ordinal differential sensitivity to target locations (indicated by d′ values) across all Ss pooled was similar to that previously found (Clement & Hosking, 1971), rs =.90. Individual Ss performed in a manner indicating a common general scanning strategy (W=.48) with idiosyncratic differences. The outcome indicated that the consistent portion of the scanning strategy was a combination of fixation effects and reading habits, with the scan operating from the upper-left comer to the lower-right corner of the display. The scan was postexposural, as the exposure duration (200 msec) was too brief to allow more than one fixation.

Pattern Perception Among Brazilians as a Function of Pattern Uncertainty and Age

Ratings of pattern goodness and of pattern preferences were made by 96 Brazilian subjects for each of 50 stimulus patterns of known pattern uncertainty. Equal numbers of male and female subjects were used in each of four age groups (9-10, 13-14, 17-18, 20-21). Ratings of pattern goodness were highly correlated with pattern uncertainty for all groups, with results very similar to those previously obtained with subjects in the United States. The youngest group showed more variability among patterns equivalent by reflection and/or rotation than did the older groups, consonant with the U. S. data. However, the two younger Brazilian groups showed even higher variability than the comparable U.S. subjects. The development of equivalency under such transformations occurred later for Brazilian as compared to U. S. students. Pattern preference was similar for all ages, and like that in the U. S., reflected preference for the least uncertain patterns.

Choice Reaction Time: The Location of Auditory and Visual Similarity.

Each of eight subjects was visually presented four stimulus classes (pairs of letters combining high or low visual and high or low auditory similarity), each class at two locations of similarity (a pair of letters in a given class requiring the same or different responses). Visual-but not auditorysimilarity affected two-choice discrete reaction time, indicating comparisons based solely on visual characteristics and stressing the important role of mode of stimulus presentation in stimulus/response compatibility.